Describes a polymerizable organic composition comprising at least one polymerizable monomer having at least two ethylenically unsaturated groups, e.g., divinyl benzene, and a polythiol monomer represented by the following general formula, ##STR1## wherein R.sub.1 and R.sub.2 are each selected from the group consisting of straight or branched chain alkylene, e.g., methylene or ethylene, cyclic alkylene, phenylene and C.sub.1 -C.sub.9 alkyl substituted phenylene. Optionally, a monoethylenically unsaturated monomer, e.g., phenoxyethyl methacrylate, and/or an anhydride monomer, e.g., methacrylic anhydride, may also be present. Polymerizates prepared from polymerizable organic compositions of the present invention have a refractive index of at least 1.57, an Abbe number of at least 33 and an initial Barcol hardness of at least 1. Also described are photochromic articles prepared from such compositions.